Rep. Ahn Cheol-soo, co-leader of the People's Party, keeps his eyes closed during a party meeting at the National Assembly, Wednesday./ Korea Times photo by Ko Young-kwon

The co-leaders of the minor opposition People's Party ― Reps. Ahn Cheol-soo and Chun Jung-bae ― resigned, Wednesday, over a high-profile corruption scandal involving three party members.

Their surprise resignations, announced at a party meeting to discuss the fate of the three, came as public confidence in the center-left party has been rapidly eroding since the scandal was made public.

The scandal is the biggest challenge yet for Ahn, a presidential hopeful, since the party founded by him in January showed a surprising performance in the April 13 general election, winning 38 of 300 seats up for grabs.

The party said later that party floor leader Rep. Park Jie-won will act as interim head until a new leader is elected at a party caucus, scheduled for February next year.

"Politics is about taking responsibility. I believe I should take all political responsibility for the case," Ahn told reporters after the meeting at the National Assembly.

The party has been reeling from the scandal since early June when the National Election Commission (NEC) accused the three ― Reps. Park Sun-sook and Kim Su-min, and party official Wang Ju-hyeon ― of accepting kickbacks from the party's PR agencies in the lead-up to the April 13 general election.

Ahn already expressed his intention to step down at a party meeting Tuesday when Wang was arrested on charges of violating the Political Fund Law, according to Rep. Park Jie-won.

Other party members asked him not to do so, but Ahn rejected their appeal, Park said.

"Ahn has taken a stringent stance over the scandal, demanding their expulsion from the party and offering his resignation," Park said during a press briefing. "Despite pleas from senior party members, Ahn remained resolute, and Chun, who empathized with Ahn on the need to take responsibility for the scandal, followed suit."

The move was viewed as Ahn seeking a turnaround amid deepening public criticism.

The scandal has been a major setback for the leader, who launched a third party with the slogan of "new politics," differentiating itself from existing politicians. It has also cast a cloud over Ahn's political future as a potential presidential contender.

In the face of increasing public criticism, the party decided Tuesday to suspend the membership of the three if they are prosecuted.

But critics still argued that the party leadership should be held accountable for mismanaging the campaign process and failing to adequately respond to the scandal.

Wang, the party's ex-deputy secretary-general, is accused of demanding a total of 216 million won ($181,000) as "rebates" from two advertising companies during the election campaign early this year, and of getting reimbursed more money than the party spent from the NEC by reporting them as election expenses.

Rep. Park Sun-sook, the party's former secretary-general, is suspected of being involved in her deputy's wrongdoing. Rep. Kim, then head of the publicity unit for the party's election campaign, allegedly signed a bogus contract and received the rebates through bank accounts of her design company, Brand Hotel.

They are being questioned by the prosecution on allegations that they broke the Political Fund Law.